Tactile roughness perception in the presence of olfactory and trigeminal stimulants

Multisensory contributions to skin-cosmetic product interactions

The human face is one of the most salient regions of the body surface. Ratings of facial attractiveness, as well as judgements of a person's age, are influenced by the appearance of facial skin (not to mention the presence/absence of wrinkles). Unsurprisingly, many consumers spend huge amounts of money on trying to protect, maintain, and/or enhance their facial appearance. As highlighted by the evidence presented in this narrative review, both the skin and the cosmetic products that many consumers use are fundamentally multisensory in nature. The complex interaction between the particular skin site stimulated and the multisensory attributes of the product (e.g., when it is applied) can exert a number of effects on an individual's mood, their emotions, as well as on their self-perception (and self-confidence), over-and-above any functional effects that the cream or lotion may have on the skin itself. In this narrative historical review, the literature on the multisensory perception of facial skin is summarized and critically evaluated. Multisensory interactions taking place between the cosmetic product, its packaging, as well as its use/application at the sensory, cognitive, and emotional levels are all discussed.

Machine learning based classification of presence utilizing psychophysiological signals in immersive virtual environments

In Virtual Reality (VR), a higher level of presence positively influences the experience and engagement of a user. There are several parameters that are responsible for generating different levels of presence in VR, including but not limited to, graphical fidelity, multi-sensory stimuli, and embodiment. However, standard methods of measuring presence, including self-reported questionnaires, are biased. This research focuses on developing a robust model, via machine learning, to detect different levels of presence in VR using multimodal neurological and physiological signals, including electroencephalography and electrodermal activity. An experiment has been undertaken whereby participants (N = 22) were each exposed to three different levels of presence (high, medium, and low) in a random order in VR. Four parameters within each level, including graphics fidelity, audio cues, latency, and embodiment with haptic feedback, were systematically manipulated to differentiate the levels. A number of multi-class classifiers were evaluated within a three-class classification problem, using a One-vs-Rest approach, including Support Vector Machine, k-Nearest Neighbour, Extra Gradient Boosting, Random Forest, Logistic Regression, and Multiple Layer Perceptron. Results demonstrated that the Multiple Layer Perceptron model obtained the highest macro average accuracy of 93 ± 0.03 % . Posthoc analysis revealed that relative band power, which is expressed as the ratio of power in a specific frequency band to the total baseline power, in both the frontal and parietal regions, including beta over theta and alpha ratio, and differential entropy were most significant in detecting different levels of presence.

Naturalistic approach to investigate the neural correlates of a laundry cycle with and without fragrance

Advancements in brain imaging technologies have facilitated the development of "real-world" experimental scenarios. In this study, participants engaged in a household chore - completing a laundry cycle - while their frontal lobe brain activity was monitored using fNIRS. Participants completed this twice using both fragranced and unfragranced detergent, to explore if fNIRS is able to identify any differences in brain activity in response to subtle changes in stimuli. Analysis was conducted using Automatic IDentification of functional Events (AIDE) software and fNIRS correlation-based signal improvement (CBSI). Results indicated that brain activity, particularly in the right frontopolar and occasionally the left dorsolateral prefrontal cortex, was more pronounced and frequent with the unfragranced detergent than the fragranced. This suggests that completing tasks in an environment where a pleasant and relaxing fragrance is present might be less effortful compared to an odourless environment.

Impacts of sensory multimodality congruence and familiarity with short use on cosmetic product evaluation

Cross-modal association between sensory modalities is a natural phenomenon in the perception of our environment. For cosmetic evaluation, touch and smell are the two major sensory modalities involved in the whole product perception. In this study, we investigate whether a specific cosmetic texture is preferentially associated with a specific fragrance: congruence between texture and fragrance. In addition, we investigate whether 1-week use of a fragrance-texture congruent or non-congruent product can influence user's whole product appreciation and well-being. We have conducted a four-test experiment with 29 participants; first in the laboratory to evaluate: six fragrances and four textures individually with free description (test 1); the same stimuli with a description with cross-modal descriptors (test 2); 10 fragrance-texture combined products (test 3); and secondly at home, two fragrance-texture combined products: one congruent and one non-congruent (test 4). Results showed that: (1) For a given texture type, specific olfactory notes are necessary to lead to a congruent cross-modal pairing product. (2) Sensory modal congruent products produce the highest hedonic response. (3) Real-life use or familiarisation with a product can influence not only the degree of cross-modal congruence but also overall cosmetic product appreciation.

Roughness perception: A multisensory/crossmodal perspective

Roughness is a perceptual attribute typically associated with certain stimuli that are presented in one of the spatial senses. In auditory research, the term is typically used to describe the harsh effects that are induced by particular sound qualities (i.e., dissonance) and human/animal vocalizations (e.g., screams, distress cries). In the tactile domain, roughness is a crucial factor determining the perceptual features of a surface. The same feature can also be ascertained visually, by means of the extraction of pattern features that determine the haptic quality of surfaces, such as grain size and density. By contrast, the term roughness has rarely been applied to the description of those stimuli perceived via the chemical senses. In this review, we take a critical look at the putative meaning(s) of the term roughness, when used in both unisensory and multisensory contexts, in an attempt to answer two key questions: (1) Is the use of the term 'roughness' the same in each modality when considered individually? and (2) Do crossmodal correspondences involving roughness match distinct perceptual features or (at least on certain occasions) do they merely pick-up on an amodal property? We start by examining the use of the term in the auditory domain. Next, we summarize the ways in which the term roughness has been used in the literature on tactile and visual perception, and in the domain of olfaction and gustation. Then, we move on to the crossmodal context, reviewing the literature on the perception of roughness in the audiovisual, audiotactile, and auditory-gustatory/olfactory domains. Finally, we highlight some limitations of the reviewed literature and we outline a number of key directions for future empirical research in roughness perception.

How Semantically Labeled Scent-Gender Associations Influence the Evaluations of Scent and Texture

Sensory evaluation can be influenced by semantic information such as gender descriptions. Gender categories are associated with tactile information (e.g., female = soft/smooth, while male = hard/rough). Feminine scents (e.g., floral) are typically perceived as soft and smooth. Thus, semantic labels of gender (feminine/masculine qualities) may influence congruent sensory evaluation (i.e., female = soft/smooth, male = hard/rough). This study examined how semantically labeled scent-gender associations influence the evaluation of scent and texture. Specifically, we examined whether “feminine” and “masculine” labels applied to neutral scents that have not been associated with gender influence scent and haptic evaluation. Participants sniffed a feminine-labeled or masculine-labeled scent embedded on soft and rough papers. They then evaluated the scent (e.g., gender perception) and texture (e.g., hedonic evaluation). The results demonstrated that participants who sniffed a feminine-labeled (vs. masculine-labeled) scent perceived it as more feminine. However, contrary to our expectations, gender labeling of scent did not influence haptic evaluation. These findings indicate that semantic labeling of scents (i.e., feminine/masculine) may alter the gender perception of a scent but not the tactile evaluation. Practical implications for (online) sensory marketing are discussed.

Gender-Dependent Crossmodal Interactions Between Olfactory and Tactile Stimulation Revealed Using the Unimodal Tactile Stimulation Device (UniTaSD)

Due to the complex stimulation methods required, olfaction and touch are 2 relatively understudied senses in the field of perceptual (neuro-)science. In order to establish a consistent presentation method for the bimodal stimulation of these senses, we combined an olfactometer with the newly developed Unimodal Tactile Stimulation Device. This setup allowed us to study the influence of olfaction on tactile perception and opened up an unexplored field of research by examining the crossmodal influence of tactile stimuli on olfaction. Using a pseudorandomized design, we analyzed how positive or negative tactile and olfactory stimuli influenced the opposing modality's perceived intensity and pleasantness. By asking participants to rate tactile stimuli, we were able to reproduce previously reported differences indicating that bimodal presentation with an olfactory stimulus increases or reduces perceived tactile pleasantness in an odor-dependent manner while highlighting that this effect appears unique to women. Furthermore, we found the first evidence for the influence of tactile stimuli on perceived odor pleasantness, an effect that is also driven primarily by women in our study. Based on these findings we believe that future neurophysiological studies, using controlled stimulus presentation can help unravel how and why olfactory and tactile perception interact in the human brain.